1. Technical Field
Some embodiments relate to integrated circuits having a functional layer including semiconductor components and metal interconnect signal lines overlying the functional components and each other. More particularly, some embodiments relate to integrated circuits having metal layers coupled as respective interconnect signal lines each having a width greater than a width of terminals of functional components to which the respective interconnect signal lines are connected.
2. Discussion of Related Art
Interconnection signal lines in integrated circuits convey signals between functional components or other parts of the integrated circuit, including power signals and information signals. For example, an interconnect signal line may convey a signal between one transistor of the integrated circuit and another transistor of the integrated circuit, or between a transistor and an output terminal, or between other parts of an integrated circuit. In an interconnect layer, signal lines may run parallel to one another in the same plane for some distance across the chip.
Interconnect signal lines have been formed of a variety of materials. In early forms of Static Random Access Memory (SRAM) and Dynamic Random Access Memory (DRAM), signals were relayed through a memory cell using substrate diffusion lines. A substrate diffusion line is formed of a doped semiconductor layer. When a signal is conducted via a signal line, however, the received strength of the signal (i.e., the strength of the signal when received at the destination) is dependent on the transmission strength of the signal and on the conductivity of the signal line. Signal lines that conduct signals via substrate diffusion have a relatively high resistivity that can reduce the received strength of the received signal. To address this problem, polysilicon or silicide layers can be formed on the doped semiconductor layers to reduce the resistivity.
Signal lines have also been formed of metal. Signal lines formed of metal have a much lower resistivity (e.g., two or three orders of magnitude lower) than substrate diffusion lines. Metal signal lines can be located in a plane above functional components of the chip and vertical plugs can connect components to the metal signal lines.
Interconnect signal lines and functional components of integrated circuits have roughly equivalent dimensions, such as roughly equivalent widths. As integrated circuits and semiconductor components have been manufactured in smaller sizes over time, the size of the interconnect signal lines, including metal signal lines, has been reduced. Recently-developed devices have an inter-transistor distance on the order of 45 nanometers and metal signal lines have been created that have a width roughly corresponding to this distance.